1. Field of the Invention
This invention relates to a semi-conducting ceramic which is useful in a jet engine igniter for a high energy, low voltage ignition system which includes a capacitor. A voltage applied to such an ignition system, when in operation, charges the capacitor and applies an increasing voltage to a spark gap of the igniter between a center electrode and a ground electrode. The ceramic of the instant invention is incorporated in the igniter so that a portion of a surface thereof is adjacent the spark gap. When the voltage applied to the igniter reaches a sufficiently high value, a spark discharge occurs between the center and ground electrodes of the igniter. This discharge ionizes the spark gap, thereby enabling a continuing current to flow until the capacitor in the ignition system is discharged. It is the discharge of the capacitor that makes this a "high energy" ignition system.
Igniters for use in high energy ignition systems are also known in which a portion of a surface of an insulating ceramic is adjacent the spark gap between the center and ground electrodes. Other factors being equal, when the ceramics are clean, the voltage required to initiate sparking is less when a semi-conducting ceramic is adjacent the spark gap than when an insulator is adjacent. It is the semi-conducting ceramic of the instant invention that makes an igniter produced therefrom, as described above, one of the "low voltage" type.